I have done a few upgrades to XenServer 7.1 with no issue. But, recently I ran into an issue where I upgraded the XenServer pool and all of the storage repositories reported that only 2 of 4 paths were connected.
All hotfixes and patches were installed, and the SAN was configured as it had been with no changes and the configuration verified. I ended up calling Citrix as I was not sure where this was coming from. Citrix support started to manually change settings via the command line and I wasn't completely satisfied why it needed to be changed, especially since this hasn't happened to any of the upgrades prior. I decided to end the call and continue troubleshooting on my own, thankfully I did.
In trying to reverse the changes by Citrix (no offense), I was able to resolve the issue. Ultimately, I disabled multi-path on each of the servers, then re-enabled multi-path. And that was it, no manual manipulation files via the console in XenCenter, easy, quick and painless.
After upgrading XenServer to 7.1.1 and you have multipath enabled, you may see a red x on your SR (storage repository) and under multi-path, it states only 2 or 4 paths.
For each XenServer host, enable maintenance mode, and disable then enable multi-path.